1. Field of the Invention
The present invention relates to capacitors and specifically, to an electrochemical double layer capacitor.
2. Technical Background
Electrochemical Double Layer Capacitors (EDLCs), or ultracapacitors, have been the subject of considerable research in recent years. The emergence of alternative energy sources and the commercialization of hybrid electric vehicles (HEVs) have created a demand for efficient, high density energy storage devices. The development of such storage devices is necessary to enable implementation of battery or fuel cell technologies in high power demand applications.
Conventional EDLCs utilize a sandwich of two metallic electrodes separated by a porous dielectric material, such as paper. This sandwich can then be rolled up to form a cylinder, known as a “jelly-roll,” with an electrolyte dispersed throughout the layers of the jelly roll. When a voltage is applied across terminals connected to each of the two electrodes, the electrolyte can ionize and an electric field on the surface of each electrode can accumulate a charge. The EDLC can store this charge until it is needed, at which time the EDLC can be discharged.
The maximum voltage that can be applied to the terminals of a given capacitor, such as an EDLC, and thus, the maximum charge that can be stored, is dependent upon the selection of components, such as the electrolyte, and the design of a given EDLC. For high power applications, such as, for example, HEVs, a large number of individual capacitors can be required. In these and other applications, the amount of space needed for a large number of capacitors can be substantial. Thus, factors such as efficiency, energy density, thermal management, electrical interconnects, control circuitry, and cost can be important in capacitor design.
There is a need to address the aforementioned problems and other shortcomings associated with conventional capacitors and energy storage devices. These needs and other needs are satisfied by the devices and articles of the present invention.